mtest: Use ntohl() when assigning IPv4-mapped addresses for IPv6 sockets.

[bms]

Summary

Direct assignments to C integer array members are in host endianness,
so preserve network endianness of a value returned by getnameinfo().

[zlei]

usr.sbin/mtest/mtest.c

162

Emm, the internet addresses ( in this case both a4 and a6 ) shall always be stored with network byte order. So is this extra ntohl really required ?

[bms]

Good catch, this was being munged elsewhere. The ntohl() for the 0x0000FFFF component is definitely needed.